1. Field of the Invention
The present invention relates to substrate processing apparatuses, and in particular to a substrate processing apparatus having a dual-chamber structure including an external chamber and an internal chamber housed in the external chamber.
2. Description of the Related Art
In semiconductor manufacturing processes for manufacturing a semiconductor device from a wafer as a substrate, a process involving chemical reactions induced by process gases tends to be widely used. The process involving chemical reactions (hereinafter referred to as “chemical reaction process”) corresponds to, for example, a process of restoring insulating films with a low dielectric constant (Low-k film) that are damaged during ashing to remove resist films by silylation gases.
In addition, vacuum processes, such as an etching process, an ashing process and a CVD process, have been frequently used in the conventional semiconductor manufacturing processes. After these vacuum processes, carrying the wafers subjected to the vacuum processes in the air can possibly produce various failures. Specifically, natural oxidation occurs on a metal layer formed through the CVD process to form an oxide film that causes conduction failures in a semiconductor device. Alternatively, the Low-k film absorbs moisture. The silylation gases (e.g., Si(CH3)3—N(CH3)2) react with a hydroxyl group (OH group) in the moisture to produce a side reaction product (Si(CH3)3—O—Si(CH3)3) that fills in trenches and via holes formed by etching.
It is therefore preferable for a wafer, especially for a wafer subjected to the vacuum process and subsequently requiring the chemical reaction process, to adopt a transfer method in which the wafer is carried in a vacuum or in an atmosphere of an inert gas, without being exposed to the air after the vacuum process, into a processing room (chamber) for carrying out the chemical reaction process to the wafer.
Conventionally, substrate processing apparatuses having a dual-chamber structure are known which include an external chamber whose inside is maintained under vacuum and an internal chamber housed in a space inside the external chamber (see, e.g., Japanese Laid-open Patent Publication (Kokai) No. 61-291965). This substrate processing apparatus maintains a vacuum in the space inside the external chamber, while introducing a process gas used for the chemical reaction process into a space inside the internal chamber, and further transfers the wafer subjected to the vacuum process through the space in the external chamber into the space in the internal chamber, thereby realizing the above-mentioned transfer method.
However, the silylation gas used as a process gas is costly, and therefore a reduction in usage of the silylation gas is required. In other words, what's required is to reduce the usage of the process gas as much as possible, and by extension to reduce the capacity of the space in the internal chamber into which the process gas is introduced.
On the other hand, the above-mentioned substrate processing apparatus having the dual-chamber structure is provided with a wafer loading/unloading port on a side wall of the internal chamber in order to transfer the wafer into the space in the internal chamber or a top lid capable of opening/closing an opening disposed on the upper part of the internal chamber. In order to transfer the wafer into such an internal chamber, an arm that transfers the wafer needs to go into the space in the internal chamber through the wafer loading/unloading port or the opening. Accordingly, there should be a clearance between the arm and components in the internal chamber to keep the arm from contact with the components, and consequently, the capacity of the space in the internal chamber cannot be reduced.